Our proposed research will deal with the uptake and integration of DNA in relation to cell membrane structure during bacterial transformation. We will test a model which suggests that the recombination step occurs in association with the membrane, possibly in the mesosome. The model predicts that permeation of transforming DNA through the membrane is concomitant with or dependent on the formation of the recombinant DNA structure. We will also examine the recurring question of DNA integration in relation to chromosomal replication. The methodology to be employed depends on analyzing the distribution of molecular forms derived from radioactive transforming DNA in extracts of tranformed cells. The subcellular localization of these DNA species in wild type and recombination-deficient mutants will be analyzed. We will continue the purification and study of the mode of action of a surface localized Bacillus subtilis endonuclease which may participate in the early processing of transforming DNA. This system is viewed as a possible model for the study of viral cell transformation in higher organisms.